T-box refers to a group of transcription factors involved in embryonic limb and heart development.

[3] Mutations in the first one found caused short tails in mice, and thus the protein encoded was named brachyury, Greek for "short-tail".

[6] The mouse Tbxt gene was cloned[7] and found to be a 436 amino acid embryonic nuclear transcription factor.

[10] In humans, and some other animals, defects in the TBX5 gene expression are responsible for Holt–Oram syndrome, which is characterized by at least one abnormal wrist bone.

[13] TBX3 is associated with ulnar–mammary syndrome in humans, but is also responsible for the presence or absence of dun color in horses, and has no deleterious effects whether expressed or not.